Myeloid-derived Suppressor Cells

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid progenitor cells that fail to differentiate into granulocytes, macrophages, or dendritic cells. These immature cells have the capacity to suppress immune responses mediated by natural killer (NK) cells and NKT cells, as well as CD8+ and CD4+ T cells. MDSCs have been suggested to have a causative role in promoting tumor-associated immunosuppression. They accumulate in the blood, bone marrow, and secondary lymphoid organs of tumor-bearing mice and cancer patients, where circulating levels of these cells have been shown to correlate with clinical stage, metastatic burden, and chemoresistance. In both mouse and human, two subsets of MDSCs have been characterized that are known as either granulocytic/polymorphonuclear (PMN) MDSCs or monocytic MDSCs.